The compound (S)-7-(1-(9H-purin-6-ylamino)ethyl)-6-(3-fluorophenyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-5-one having Formula I:
is a phosphoinositide 3-kinase (PI3K) inhibitor useful in the treatment of various diseases including cancer. The compound of Formula I, as well as its preparation and use, have been described in US Pat. App. Pub. No. 2011/0015212, which is incorporated herein by reference in its entirety. For the development of a drug, it is typically advantageous to employ a form of the drug having desirable properties with respect to its preparation, purification, reproducibility, stability, bioavailability, and other characteristics. Accordingly, the crystalline forms of the compound of Formula I provided herein help satisfy the ongoing need for the development of PI3K inhibitors for the treatment of serious diseases.